A/C compressor won't charge

I've got a 91 1500 truck with a brand new a/c compressor, I went to charge it and can't. I bought a kit from the autoparts store and hooked it up to the compressor and turned to valve to release the refrigerant and it's like it's clogged or something. It never goes in! Is there something I'm missing with this?

Make sure you are adding freon to the "suction" side of the compressor.

Also, did you add the correct oil to the compressor? There is an automotive AC forum out there you might want to check out. I don't have the URL.